/* Copyright  (c) 2002 Graz University of Technology. All rights reserved.
 *
 * Redistribution and use in  source and binary forms, with or without 
 * modification, are permitted  provided that the following conditions are met:
 *
 * 1. Redistributions of  source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in  binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *  
 * 3. The end-user documentation included with the redistribution, if any, must
 *    include the following acknowledgment:
 * 
 *    "This product includes software developed by IAIK of Graz University of
 *     Technology."
 * 
 *    Alternately, this acknowledgment may appear in the software itself, if 
 *    and wherever such third-party acknowledgments normally appear.
 *  
 * 4. The names "Graz University of Technology" and "IAIK of Graz University of
 *    Technology" must not be used to endorse or promote products derived from 
 *    this software without prior written permission.
 *  
 * 5. Products derived from this software may not be called 
 *    "IAIK PKCS Wrapper", nor may "IAIK" appear in their name, without prior 
 *    written permission of Graz University of Technology.
 *  
 *  THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESSED OR IMPLIED
 *  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 *  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 *  PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE LICENSOR BE
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 *  OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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 *  OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 *  POSSIBILITY  OF SUCH DAMAGE.
 */

package demo.pkcs.pkcs11;

import java.security.NoSuchAlgorithmException;
import java.security.Signature;

import iaik.asn1.structures.AlgorithmID;



/**
 * This class is an adapter to enables an application to use a different
 * implementation than the standard implementation with the IAIK-JCE.
 *
 * @author <a href="mailto:Karl.Scheibelhofer@iaik.at"> Karl Scheibelhofer </a>
 * @version 0.1
 * @invariants
 */
public class AlgorithmIDAdapter extends AlgorithmID {

  /**
   * The delegate object to use, if no concrete implementation is set for a
   * certain engine class.
   */
  protected AlgorithmID delegate_;

  /**
   * This is the signature engine to use for this object.
   */
  protected Signature signatureEngine_;

  /**
   * Creates a new AlgorithmIDAdapter that uses the given delegate object
   * to get the .
   *
   * @param delegate The object to get other implementations from,
   *                 implementations not provided by this object.
   * @preconditions
   * @postconditions
   */
  public AlgorithmIDAdapter(AlgorithmID delegate) {
    super(delegate.getAlgorithm());
    delegate_ = delegate;
  }

  /**
   * Set the implementation to use as signature instance.
   *
   * @param signatureEngine The implementation of the signature class to return
   *                        upon a call to getSignatureInstance(). If null, the
   *                        implementation is unset.
   * @preconditions
   * @postconditions
   */
  public void setSignatureInstance(Signature signatureEngine) {
    signatureEngine_ = signatureEngine;
  }

  /**
   * If a concrete signature implementation was set using
   * setSignatureInstance(Signature), this method returns this. Otherwise, it
   * delegates the call to the delegate of this object.
   *
   * @return The signature engine to use for this algorthim.
   * @exception NoSuchAlgorithmException If there is no signature
   *                                     implementation for this algorithm.
   * @preconditions
   * @postconditions
   */
  public Signature getSignatureInstance()
      throws NoSuchAlgorithmException
  {
    return (signatureEngine_ != null) ? signatureEngine_ : super.getSignatureInstance();
  }

  /**
   * If a concrete signature implementation was set using
   * setSignatureInstance(Signature) and the provider name is null, this method
   * returns this set signature implementation; otherwise, it delegates the call
   * to the delegate of this object.
   *
   * @return The signature engine to use for this algorthim.
   * @exception NoSuchAlgorithmException If there is no signature
   *                                     implementation for this algorithm.
   * @preconditions
   * @postconditions
   */
  public Signature getSignatureInstance(String providerName)
      throws NoSuchAlgorithmException
  {
    return (providerName == null) ? getSignatureInstance() : super.getSignatureInstance(providerName);
  }

}